Portable electronic devices in the market, such as handheld electronic devices, usually adopt batteries as the power source. Usage time (i.e. the time your battery will run before it must be recharged) and standby time are the important considerations when buying a portable electronic device. Thus, all the manufacturers have considered extension of usage time and standby time as an important issue for the development of portable electronic devices.
Attending with the development and wide spreading of telecommunication technologies, social distance between people is dramatically reduced. In the fast-paced modern society, for the purposed of catching the instant information against time, the handheld electronic devices with multi-function, such as personal digital assistant (PDA), module phone, and etc., came out in the market to execute various information, e.g. voice, text message, video and word processing, in a limited time period simultaneously. It is noted that other than the trend of slimmer, smaller, and lighter to make the handheld electronic device easy to carry and improved the overall performance, it is also an important topic to extend the usage time and standby time of the handheld portable device without connecting to a power source.
Generally, the most power-consuming condition for the handheld electronic device, other than the specific function such as talking on the phone, should be the usage of the display to show the information. In order to reduce the unnecessary power-consumption, how to control the power supply for the display, especially when the handheld electronic device is standby, is an important topic. However, on/off of the display in the traditional handheld electronic device is controlled by a specific switching button or by setting a timing module with a predetermined time period. The switching button, which occupies some of the already limited space within the handheld electronic device, may enhance the cost of mechanical design and elements. In addition, it is troublesome for the user to remember touching the switching button every time when he wants to enable the power-saving function. On the other hand, when the timing module is used, the user cannot freely control the on/off condition of the display, which makes the operation less convenient.